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Once upon a time, before humans diverged from chimpanzees or the Grand Canyon had been carved out of its rock, an extraordinary bird walked and flew the earth in the area we now call Nebraska. The bird stood some four feet tall and had a wingspan of more than six feet. Its Miocene neighbors included the saber-toothed deer—which sounds like a Monty Python joke but really existed—and prehistoric versions of the rhinoceros and the camel. The camels and the weird deer are gone, but astonishingly, the bird—or its structurally identical relative—is still around. We know it as the sandhill crane, and while this most ancient of birds would be a marvel in any form, it happens to participate in one of the great mass migrations on the planet, making a journey through space that is as remarkable as its journey through time.

Between February and April, more than half a million sandhill cranes crowd through a short stretch of the Platte River of central Nebraska, staging for an odyssey that ends as far north as the tundra of eastern Siberia. Along the Platte, having already flown some 600 miles from the American Southwest, they will gorge themselves on the abundant remains of numerous cornfields, gaining 20 percent of their body weight in anticipation of the thousands of miles still before them. But despite their frenzied feeding, these social birds—who mate for life and remain behind if their mate is sick or injured—still find time to do the thing for which cranes are most famous: dance.

Departing New York City for Omaha in peak crane season, I can’t help marveling at my own lucky journey through space and time. Ever since a stranger’s chance comment about the birds of Central Park led me to an introductory birdwatching class at New York City Audubon 15 years ago, I have been in love with birds and perpetually grateful to them for opening up to me the hidden wild places in my city, my country, my planet, and, most surprisingly of all, myself.

From Omaha I drive 182 miles west to Kearney, Nebraska. The moon is nearly full, massive and orange. Part of me simply decides that this is what happens when you fly to the middle of America to look at cranes; things get bigger and more beautiful, or at least noticed with a new eye. But the next day the moon is on the cover of the Omaha World-Herald, and I learn that it is a “supermoon,” closer to the earth than at any time in the past 20 or so years. Back home I might have seen a fat moon rising over the Empire State Building, but to have the oldest birds on the planet intersect with it, and with me, I need to travel 1,300 miles, to a particular place at a particular time.

The island I live on is sometimes called “the crossroads of the world,” but that depends on your definition of “world”—and “crossroads.” Look back into the 19th century, add in the overlapping trails of Pawnee and Sioux, millions of bison, the Oregon Trail, the Union Pacific Railroad, and the Central Flyway for migratory birds, and suddenly the middle of Nebraska, which is smack in the middle of the United States, has a claim to make as the literal and spiritual intersection of a vast array of competing forces.

I’m in a hurry to meet the birds, so I welcome the 75 mile-per-hour speed limit on Interstate 80, which follows the contours of the Platte River—just as the Mormon Trail, the Oregon Trail, and the Pony Express once did. In those days Nebraska was considered part of the “the Great American Desert,” little more than a wild corridor to greener pastures in the west. When Francis Parkman passed through the Nebraska territory in 1846, making notes for The Oregon Trail, he observed, along the banks of the Platte, the “shattered wrecks of ancient claw-footed tables” that desperate emigrants had, in exhaustion, “flung out to scorch upon the hot prairie.”

The unrelieved sameness of I-80 does little to recall those days. Only the big moon evokes the world as it was—and of course the cranes, which I begin to see amid the stubble of cut cornfields along the side of the road, 200 or so yards back from the highway. They leap into the air, squabble, take off, land, toss the occasional stick into the air with their bills, bow from time to time, and most of all feed with their heads down, their long necks extended.

Corn-made fuel has a complicated history for humans, but raw corn, which can make up more than 90 percent of the sandhill crane’s diet, will power the birds for several thousand miles, and I shudder to think what would happen if more efficient combines are created that eliminate the gleanings the birds feast on, though their omnivorous opportunism—they’ll eat seeds, berries, insects, earthworms, mice, snakes, lizards, and frogs—has preserved them in the past. But the concentrated food of farms helps compensate for the lost foraging areas and fast-running rivers once abundantly at their disposal.

For now there is plenty of corn and there are plenty of cranes. I almost don’t want to see them yet—we have a date for early evening, when I’ll be in a blind at Audubon’s Rowe Sanctuary, waiting for the sun to go down and the cranes to come out. But I fight this artificial impulse to falsify what I’m actually seeing. These are not backstage actors whose show won’t start till curtain time and I’m in my box; they’re big, gray, semi-graceful birds that live alongside the industrialized world and whose leaps and jabs are—admit it!—the dancing I’ve been dreaming about. They’re not the ballet ostriches of Fantasia, they’re wild animals that, despite deep social instincts, are perfectly capable of pecking their siblings to death when small, and that often do—a trait shared with other crane species, not to mention eagles and egrets.

For all the cranes’ seemingly human attributes—their voices change as they age, they paint themselves with mud for camouflage, they even go bald as they get older—it’s the wild otherness of the birds, as with all wildlife, I try to honor. At the same time, it isn’t only wild otherness that sustains them. There are 10 times more sandhill cranes along the Platte now than there were in the 1940s (an astounding 500,000 birds); sanctuaries, river management, and vast fields of corn help explain the population explosion, though the flipside of the agricultural bonanza is the diversion of water that, in the Platte, used to flow far wider and far faster, scouring its islands clear of bushes and trees, which was essential for keeping the river a suitable roosting spot for skittish birds ever on the lookout for coyotes and other predators.

Today heavy machinery clears islands in the Platte once scoured by spring floods, work that Audubon’s Rowe Sanctuary undertakes at vast cost, along with its education and conservation efforts. Nebraska, its highway signs inform me, is “Home of Arbor Day,” but sometimes removing trees is as environmentally important as planting them.

This is something Bill Taddicken, Rowe Sanctuary’s genial, mustached director, understands well. I meet Taddicken at the Best Western Mid-Nebraska Inn and Suites in Kearney, where I’m staying with other crane enthusiasts. He’s briefing us for an evening in the blinds. One of the things I admire endlessly about men like Taddicken is that—along with running an education center, recruiting volunteers to help shepherd 15,000 birder-tourists who come each spring, fighting water diversion projects without alienating farmers, raising money for farmland that might be added to the sanctuary’s patchwork plots, and a host of unglamorous bureaucratic tasks that go unsung into conservation—he still breaks into a broad grin when describing crane migration. He all but bursts into poetry as he evokes that first glimpse of birds descending—“little specs out of the ether” that grow more distinct and more numerous until they come down as if “poured out of a bucket.” Their landing, however, is delicate: “like a dandelion seed coming down.”

Soon we are in a blind—a little wooden hut the size of a one-room schoolhouse, with small, square, head-high openings chopped out for viewing. The blind is perched right above the Platte, and we can see and hear the river rushing. The sun is still going down—it’s important to be in the blinds early so we do not spook the birds; we will creep out after dark, when the cranes have settled in the river, where they roost midstream. Camera lights are taped over and I haven’t even bothered to bring mine—who wants to be the guy with the accidental flash who sets off a chain reaction that incites 20,000 birds? It is, besides, a gloriously documented spectacle.

The birds are already filling up the fields beside the river, where many thousands are gathering; they’ll transfer en masse to the river once it gets dark. And suddenly it is dark enough and the cranes begin to come. These are not the roadside birds I saw on my drive, 200 yards off the highway. Their wings are as wide as I am tall; their bodies are as long as my eight-year-old daughter. Their stick legs, stretched behind them as they fly, drop under them like landing gear as they come down. I am a guest in their world now. It’s their highway I’m parked beside.

There are so many of them, circling, landing, shaking their bustles, taking off again, flying into and out of and through the restless merging flocks, that it is hard to focus on any one individual. I feel like a dog chasing too many rabbits. Looking left and right there are perhaps five miles of river in view, which according to Taddicken can hold about 100,000 birds.

Strangely, this gives the stretch of river something in common with Central Park in Manhattan. It was the superabundance of migrating songbirds that knocked me over when I first began birding there; only later did I learn that, because birds flying over modern cities have so few green options, it was an artificial profusion, creating a false impression about the global health of birds. In Nebraska there used to be about 200 miles of river suitable for cranes whereas now they’re crowded into a 50-mile stretch between Grand Island and Kearney. Thanks to numerous dams, only about 30 percent of the Platte’s water makes it as far as the Rowe Sanctuary, limiting the cranes’ habitat even more.

No great natural spectacle comes without a political or a philosophical backstory. How many cranes should there be? Several states now either allow a hunting season or are debating one—and without question sandhill cranes have made an extraordinary comeback. Of course some populations do better than others, some migrate, others stay put and are more vulnerable. How permanent is their newfound success—dependent as it is on strenuous conservation efforts and an uneasy alliance with farmers—and how vulnerable is a population of huge birds that produce only one or two young a season, and that must hopscotch over ever-urbanized migratory pathways? These questions are important, for they explore how fully cranes—and all birds, really—live today inside the artificial world. The wide, fast rivers that once sustained the cranes will never be returned to them. Their ability to be wild is a test of our ability to manage the world we have altered, which is to say it is a test of our humanity, and so we are bound together, needing each other in complex ways we’re only beginning to understand.

The noise surprises me, as if I’d imagined migration as a silent movie, but the birds call to one another constantly, a cacophony of loud croaks and cries.

“Cup your ears,” whispers Taddicken. I go farther and close my eyes.

Each complex, trilling call, strung out of beads of sound, can carry for a mile and seems both high and low. The cumulative effect is like thousands of ancient doors creaking open, as much vibration as voice, echoed not only by the rushing river but your own blood.

Suddenly there’s nothing scientific or ornithological about my observations. I’m part of the flock, and I understand an aspect of Great Plains mysticism I often encounter in Nebraska writers as disparate as Willa Cather and the scientist Loren Eiseley, whom I read as a boy, not realizing he was from Nebraska until Matt Harvey from the Spring Creek Prairie Audubon Center gives me a copy of The Loren Eiseley Reader. In that collection there’s an essay in which Eiseley strips off his clothes and floats in the Platte River, despite his terror of water after a near-drowning accident as a child. Eiseley lets the broad, shallow river, famous for quicksand, take hold of him, and has “the sensation of sliding down the vast tilted face of the continent,” feeling a kind of ancient earth memory more in tune with native American religion than the detachment expected from an anthropology professor.

I emerge from the blind with my senses confused. The wind has kicked up, the clouds have obliterated the supermoon, but the superbirds are still aloft, making a racket. As we file out quietly to crunch across a field and back to our cars in cold darkness, temperature plunging, thousands of cranes are streaming restlessly above us, dark shapes against the deeper darkness of the sky. They should have roosted by now, but there’s a kind of anxious tension in the air. I lie on my back and look up, feeling like Eiseley in his river, but it’s a river of birds.

The birds settle down eventually; when we return to the blinds next morning before dawn, we find the cranes crowded on sandbars in cocktail party clusters or standing in water up to the knot in their long legs that looks like a knee but that, in one of the quirks of avian physiology, is really an ankle. The cranes seem calm in the pale light. A bird raises its wings in a sort of lazy flap, almost like a yawn, before rising into the air; others seem pulled after it by invisible strings, though there’s no hurry. Some land again, and those that don’t circle the river several times before flying off. High above them, the brightening air is full of milling birds as if someone had stirred the sky with a stick.

There’s more to see as the sun comes up—a log floating past that turns into a beaver; some coots, a muskrat by a clump of reeds—but I miss the thrumming frenzy of the night before. The rest of the world returns to focus. Two power lines stretched across the river take a toll of crane lives every spring but cost too much to bury.

Outside the blind I meet Michael Farrell, who produces documentaries for Nebraska public television. Farrell informs me that the birds were restless the night before because the river, often too low for the cranes, is too high for them now—there was 40 percent more snow pack in the Rockies, which meant an opening of dams to make room for the increased melt, which in turn raised the level of the river, a chain reaction of man and nature that affects the crane’s roosting habits.

Farrell has a grizzled moustache, glasses and a mixture of outdoor unpretentiousness, activist outrage, and professorial intensity not uncommon among the environmentally engaged. He pours out a dizzying array of Nebraska history, the sorrows of the Oregon Trail that sowed cholera for Native Americans, the fierce community battles that began in the 1970s over water diversion along the Platte, something about the Salt Creek tiger beetle that I don’t entirely catch. Farrell also tells me that for the past 13 years he’s come to Rowe Sanctuary on the first day of spring, ever since he and his family scattered his wife’s ashes from the blind we’ve just been in. His wife loved the annual migration and had said to him, as she was dying, “Remember me when the cranes come.”

It is, I realize, the first day of spring. And I realize that a blind for bird observation can also be sacred space. It is a humbling recognition that reminds me to look at nature—at everything, really—two ways, attuned to the practical, political, and scientific and, at the same time, the mysterious, the personal, and the beautiful.

On my drive back to the Omaha airport, I stop at a field a few exits off of I-80, not far from Kearney. I’ve received a murmured suggestion, more like a gambling tip, that I look there for a “big white bird,” code for a highly endangered whooping crane. Like sandhills, whoopers are an ancient species but proof that nature does not have a first hired, last fired policy—there were only 15 individuals in 1941, and even today, after vigorous conservation and breeding efforts, there are fewer than 400 whooping cranes left in the wild.

Just as sandhills are the most numerous, whoopers are the scarcest of the world’s 15 species of cranes, but the two species overlap at various points on their journey, and just a few weeks after I leave Nebraska, 11 are seen in the Platte from the blinds at Rowe. I’ve long wanted to see whooping cranes, snow-white birds with black wingtips that, at five feet, are the tallest North American bird, as well as one of the rarest. It is because of the whoopers’ endangered status that Federal money can be used to maintain the Platte, which in turn benefits sandhills and other species. It is the whooping cranes that carry their far more numerous cousins on their endangered backs.

I fail to find the whooper at the designated exit, though there are plenty of sandhills grazing and flapping. Nothing demotes a magnificent bird faster than redefining it as “not the bird I’m looking for.” Still, I know I will pine for these birds as soon as I’m back in New York. And both species should be held together in the mind, the white bird somehow the shadow of the gray one, a reminder of the threat of extinction in the midst of abundance, and of the double vision required by birdwatching.

This story originally ran in the January-February 2013 issue as "Lords of the Dance."